Immunization against bacterial or viral infection has greatly contributed to relief from infectious disease. Generally, immunization relies on administering an inactivated or attenuated pathogen to the subject to be immunized. For example, hepatitis B vaccines can be made by inactivating viral particles with formaldehyde, while some polio vaccines consist of attenuated polio strains that cannot mount a full-scale infection. In either case, the subject's immune system is stimulated to mount a protective immune response by interacting with the inactivated or attenuated pathogen. See, e.g., Kuby, 1997, Immunology W.H. Freeman and Company, New York.
This approach has proved successful for immunizing against a number of pathogens. Indeed, many afflictions that plagued mankind for recorded history have been essentially eliminated by immunization with attenuated or inactivated pathogens. See id. Nonetheless, this approach is not effective to immunize against infection by many pathogens that continue to pose significant public health problems. In particular, no vaccine presently exists that has been approved for immunization against C. trachomatis infection. The absence of such a vaccine presents significant public health problems.
For example, C. trachomatis infection is the most common sexually transmitted disease (STD) worldwide, with more than 500 million people throughout the world infected each year, approximately 4 million of which occur in the United States. See Jones and Batteiger, 2000, Principles and Practice of Infectious Diseases, Mandell, Bennett and Dolin R, eds., Churchill Livingstone, Philadelphia, pp. 1986-1989. The U.S. Centers for Disease Control and Prevention (CDC) estimates that these infections result in an estimated cost to Americans of $2 billion a year. About 75% of women and 50% of men infected with C. trachomatis are asymptomatic, resulting in large populations of untreated individuals. See Karam et al., 1986, J Infect Dis 154:900-3. Up to 40% of women with untreated C. trachomatis infection will develop pelvic inflammatory disease (PID). Because PID can cause scarring of the fallopian tubes, 20% of infected women will become infertile, 18% will experience debilitating, chronic pelvic pain and 9% will have a life-threatening ectopic pregnancy. If a pregnant woman becomes infected with C. trachomatis and is not treated, her baby has a 50% chance of developing conjunctivitis and a 20% chance of pneumonia. Very recently, C. trachomatis infection has also been identified as a risk factor for invasive squamous-cell carcinoma of the uterine cervix and a complicating factor in HIV-1 infection. See Koskela et al., 2000, Int J Cancer 85:35-9 and Kimani et al., 1996, J Infect Dis 173:1437-44.
When C. trachomatis infection is detected, antibiotic therapy can usually effectively eliminate the infection. However, these therapies do not always resolve persistent infections or affect established pathologies, such as autoimmunity. See Dean et al., 2000, J. Infect. Dis. 182:909-916. Further, issues related to unnecessary antibiotic use and costs associated with frequently screening asymptomatic individuals in an effort to decrease transmission make a compelling argument for developing systems for inducing protective immune responses. Over three decades of efforts to protect individuals from C. trachomatis infection, however, have been unsuccessful. See, e.g., Stagg, 1998, Mol Med Today 4:166-73 and Beagley, 2000, J Reprod Immunol 48:47-68. Thus, there remains an unmet need for methods and compositions that can immunize against C. trachomatis infection. These and other unmet needs are provided by the present invention.